In the first of a two-part series on the National Gallery of Ireland refurbishment, David Clarke outlines the many structural engineering challenges involved and radical solutions implemented to best display the gallery’s 15,000 works of art
Civil

The historic wings of the National Gallery of Ireland – the Dargan wing (1864) and the Milltown Wing (1901) – have long held works of fine art. But through 150 years of decay and alterations, the gallery had become disjointed and dysfunctional, no longer providing a frame to support and enhance the artwork within, nor to inspire new Irish creativity.

The client’s brief for this project was: 1) to develop a coherent and accessible circulation system through the various layers of the gallery, and 2) to upgrade and restore the historic wings to the highest international standards for environment control, lighting and security systems.

While the first seemed the most structurally challenging, the second required even more creative solutions. With no humidity or pest control, an open well discovered under timber floorboards, clinker concrete flooring or timber joists inadequate for reasonable loads, insufficient and ineffective lighting… this was a wildly outdated environment for preserving and displaying 15,000 works of fine art.

Those initial client concerns surfaced immediate obstacles. Radically upgrading the environmental standards would require incorporating equipment without damaging or detracting
from these preserved historical buildings. The confined site is immediately adjacent to the Irish Parliament, buildings with significant security requirements, and city-centre traffic. Though the original historical drawings were accurate, the intervening works were not adequately documented. Engineering solutions became the obvious key to the success of the project.

Creativity and innovation from start to finish


Construction of a standalone Energy Centre was necessary, due to the complexity and magnitude of the services required to facilitate a fully modernised art gallery. To preserve the relationship between the buildings on this confined site and the architectural history within and immediately surrounding it, this centre sinks invisibly under the existing external front forecourt area, buried up to 8.5m underground.

New concrete substructure trenches expand through all areas of the historic wings, varying in depth such that the original foundations required concrete underpinning up to 4.5m in depth. This Energy Centre is the unseen heart of the National Gallery, hidden trenches feeding the complex like a system of veins and arteries. Life has been restored to the old buildings.

The design of the project was undertaken in BIM (building information modelling) within PUNCH Consulting Engineers, modelling all of the National Gallery’s buildings from historical drawings and investigative works undertaken on site. Following the building of this model, the 3-D services design was incorporated into and co-ordinated within this structural model, creating intentionally invisible routes for all services throughout the buildings.

Where possible, the original historical flooring received strengthening works to increase their capacity to achieve modern design code magnitudes. These works included replacing the clinker slab with modern reinforced concrete and introducing additional steel beams to decrease the spans of existing timber joists. The roof lights have been completely replaced to enhance the visual and thermal quality of the galleries.

The Dargan Wing laylight frame has been also restored and the glass panes are glued to a new steel frame supported by the existing one to improve the post fracture behaviour of the glass.

By the creative nature of the design solutions, visitors will move through the National Gallery complex without disruption. None will see any compromises to the beautiful conservation of the historic galleries, yet the observant visitor might begin to catch glints of creative innovation.

Elegance and detailing created and revealed


Photo: Marie Louise Halpenny

Ironically, in a complex dedicated to creative beauty, these two buildings’ complementary elegance was not only disused, but thwarted. When the Milltown wing siting (1901) encroached on the windows of the original Dargan building, a stunningly simple lightwell of glazed white tiles was designed. Yet during a previous renovation, the counterpart windows of the Dargan wing were bricked up, and this beautiful interaction was obscured, the intervening space disused and neglected.

Now, not only is the intended interaction between these two buildings revealed, and the historic lightwell solution reinstated, new engineering creativity has enabled a further gallery space in what had long been a dingy alleyway.

Some 23 structural glass fins that span the 7- to 9-metre gap between the two historic wings support the glass roof of the new Sculpture Court. These triple-laminated toughened glass fins minimise the visual impact of the structure and achieve a more elegant ‘external, open quality’ in the space below. The glass fins are laterally stabilised by the top glass plane. The post fracture behaviour has been the main structural challenge of this roof.

An alternative load path without including any supplementary element on the system has been created. In the case that the all three glass sheets of a fin are broken, the fin is supported by a stainless-steel plate glued to the top of the beam and bolted to both end shoes that acts as a catenary.

The lateral forces induced by this plate are too high to be resisted by the existing masonry of the Dargan Wing. In this case, the end shoe develops a plastic hinge and the lateral forces are transferred by an edge steel profile to the adjacent glass fins. In that way, the lateral forces are enclosed in the system and only vertical loads are transferred to the masonry. Nonlinear FE analysis and full scale tests demonstrate this behaviour.

Two fair-faced concrete lift cores stand within the same internal open space. These new structural elements are founded at the lower-ground-floor level within the maze of services, elegantly extending to and projecting through the glazed roof. Wrapping around the West lift core is a fair-faced concrete staircase, which cantilevers from the wall. The fluid, graceful structural solution invites a flowing journey through the galleries.

Sustainability past uncovered, future preserved


As well as uncovering the original features of sustainable natural lighting, in the lightwell and windows of the Sculpture Court, the long disused roof lights to the Milltown and Dargan first-floor galleries have been revealed. Micro louvres within the new glazing panels maintain high levels of natural light while complying with curatorial requirements, with UV transmittance below 1%.

These produce a glazing g-value of 0.14, reducing solar gain by 80% and heat transfer by almost 70%. Even the invisible spaces — dedicated to conservation and preservation — benefited from new roof-light designs.

Embedded in the Energy Centre, an advanced central control system reduces air conditioning flow rates resulting in significant energy savings. A new chiller system recovers heat loss, operates as an air source heat-pump and allows for large proportions of the electrical load to be transferred to the night, smoothing demand on the grid.

Sustainable concrete, with 50% ground granulated blast-furnace slag (GGBS), was used throughout the project. Demolished sections of historic stone, brick and glass from the building were documented and stored by the client for future use in other conservation projects, maximising the social impact of the project throughout the country.

At the heart of this project, by carefully restoring these beautiful old buildings, their embodied energy – resources, materials, labour and creative solutions from past minds, poured into constructing and maintaining the Galleries and their contents — is conserved, but also preserved for generations to come.

Value a nation’s priceless treasures for free


Photo: Marie Louise Halpenny

The Irish Government committed to this project before the economic crisis, but its investment continued weathering ten years of Ireland’s financial uncertainty. With 10,000m2 of floor area, the engineering and structural solutions of this project resulted in an extremely viable contract value.

The non-financial value is inestimable. The Irish Government believes our heritage should be available to all, so entry to the galleries is free. Yet visitor numbers dropped by 17% to 630,000 yearly while the Historic wings were closed. The foreseeable numbers for this coming year are a dramatic increase, in excess of 1,000,000: the most popular free tourist
attraction in Ireland.

Photo: Marie Louise Halpenny

Masterpieces by Caravaggio and Canova, Rembrandt and Rubens, Turner, Titian, Velázquez, Vermeer and Van Gogh hang once more alongside the most important works of Irish art — Jack B Yeats’ Men of Destiny, Augustus Nicholas Burke’s Connemara Girl and portraits of past tyrants, the tyrranised and the triumphant of the growing Irish nation. Irish artistic identity lies within these walls.

Ultimately, we exceeded client expectations by meeting not just their brief, but their aspirations: providing all of the requirements of a modern gallery, yet with all services completely hidden within the beautiful skin of the original historic buildings.

Photo: Marie Louise Halpenny

As it opens again, the museum is more than just a series of blank boxes, frames housing beautiful pieces. The historic-wing buildings themselves quietly reveal the ingenuity of Irish creatives such as William Dargan, the visionary engineer who began this collection, and the Countess of Milltown, who presented 200 works of art to the National Gallery from Russborough House, Co Wicklow.

The emotional, historical and cultural value of the National Gallery of Ireland lies not just in the works it houses, but embodied in the very skin of these historic buildings. They hold both the era of a developing national Irish artistic identity, and now also this new era, committed to redeeming and restoring Ireland’s best, hoping to inspire new creatives.

Read the second part of this article.

Author:
Dave Clarke BA BAI MSc CEng MIStructE MIEI, technical director, PUNCH Consulting Engineers

In the second part of this two-part series, Chris Croly of BDP outlines challenges of providing a close control environment for the protection of priceless artwork in a historic space.

http://www.engineersjournal.ie/wp-content/uploads/2017/08/National-Gallery-1-1024x580.jpghttp://www.engineersjournal.ie/wp-content/uploads/2017/08/National-Gallery-1-300x300.jpgDavid O'RiordanCivilconstruction,heritage,PUNCH Consulting Engineers
The historic wings of the National Gallery of Ireland – the Dargan wing (1864) and the Milltown Wing (1901) – have long held works of fine art. But through 150 years of decay and alterations, the gallery had become disjointed and dysfunctional, no longer providing a frame to support...